Ajax Code works in IE9 but nor works in other browser

<script type="text/javascript" language="javascript">
        var xmlHttp;
        function SoapCall() {

            // creatng the xmlHttp object
            if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari
                xmlHttp = new XMLHttpRequest();
            }
            else {// code for IE6, IE5
                xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
            }
            // Calling the web service using post and true means asynchronous call
            xmlHttp.open("post", "http://www.webservicex.net/CurrencyConvertor.asmx", true);
            // Setting the request header to let the web service identify the soap request we would be sending

            xmlHttp.setRequestHeader("Content-Type", "text/xml; charset=utf-8");
            xmlHttp.setRequestHeader("Origin", "http://www.webserviceX.NET");
            xmlHttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");

           // xmlHttp.setRequestHeader("Access-Control-Allow-Origin", "http://172.27.47.144");
            xmlHttp.setRequestHeader("SOAPAction", "http://www.webserviceX.NET/ConversionRate");

            var soapRequest = '<?xml version="1.0" encoding="utf-16"?>' +
'<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">' +
  '<soap:Body>' +
    '<ConversionRate xmlns="http://www.webserviceX.NET/">' +
      '<FromCurrency>USD</FromCurrency>' +
      '<ToCurrency>INR</ToCurrency>' +
    '</ConversionRate>' +
  '</soap:Body>' +
'</soap:Envelope>';


            xmlHttp.onreadystatechange = function () {
                if (xmlHttp.readyState == 4 && xmlHttp.status == 200) {
                    alert(xmlHttp.responseText);
                }
            }
            xmlHttp.send(soapRequest);


        }
    </script>